In late 2018, you gained the ability to transfer your Capital One miles to one of airline programs.
Currently, if you have a Capital One Venture Rewards Card or VentureOne Rewards Card or a Capital One Spark Miles Business Card or Capital One Spark Miles Select Business Card you can transfer your miles them to one of 14 airline loyalty programs, most at a rate of 2 Cap One Miles to 1.5 airline miles. (2:1.5). There are some exceptions as to the transfer rate.
Starting tomorrow, Capital One is adding 2 hotel partners as transferees. These hotel partners aren’t very sexy, but it’s a start. Starting tomorrow 2/4, you can transfer your Capital One Rewards to Wyndham Rewards and Accor Live Limitless (whose top properties are Fairmonts).